Express your answer as a mixed number simplified to lowest terms. $15\dfrac{1}{4}-11\dfrac{5}{7} = {?}$
Find a common denominator for the fractions: $= {15\dfrac{7}{28}}-{11\dfrac{20}{28}}$ Convert ${15\dfrac{7}{28}}$ to ${14 + \dfrac{28}{28} + \dfrac{7}{28}}$ So the problem becomes: ${14\dfrac{35}{28}}-{11\dfrac{20}{28}}$ Separate the whole numbers from the fractional parts: $= {14} + {\dfrac{35}{28}} - {11} - {\dfrac{20}{28}}$ Bring the whole numbers together and the fractions together: $= {14} - {11} + {\dfrac{35}{28}} - {\dfrac{20}{28}}$ Subtract the whole numbers: $=3 + {\dfrac{35}{28}} - {\dfrac{20}{28}}$ Subtract the fractions: $= 3+\dfrac{15}{28}$ Combine the whole and fractional parts into a mixed number: $= 3\dfrac{15}{28}$